1. Field of the Invention
This invention relates to an apparatus for exercising the human body. More particularly, the invention relates to an exercising machine in which the force placed on the user of the machine can be rapidly varied by the user while the user is exercising with the machine.
2. Description of the Prior Art
Weight lifting devices and exercising machines are well known in the prior art. Individual weights can be added to the machines and exercising devices to increase the force applied to the body of the user or weights can be removed to decrease the force applied to the user. However, such an increase or decrease in weight cannot be accomplished by the user while he is actually using the machine and requires that the user remove himself from the machine and add or remove weights to the machine or that he employ another person to vary the weight load on the machine.
U.S. Pat. No. 4,272,074 discloses a body building apparatus having a rectangular frame which is pivotally mounted to permit the frame to assume a variety of positions with respect to the horizontal. The apparatus includes a platform slidably mounted on the frame to seat the user, along with grips on which the user may pull to move the platform against his own weight, and an adjustable spacer for fixing the incline of the frame with respect to the horizontal to vary the resistance of the platform to movement. Thus, to vary the force required to move the platform or the resistance of the platform to movement, it is necessary that the frame be pre-adjusted prior to the user mounting the frame, and the user cannot vary the resistance of the platform to movement while actually operating the frame.
U.S. Pat. No. 4,176,836 discloses a variable resistance exercising apparatus and method whereby the resistance encounter by the body part or parts being exercised is varied by moving the body part or parts along a discretely curved incline, whereby the resistance varies automatically and instantaneously commensurate with the sine of the angle of the incline. The apparatus includes a chair or movable platform for holding the torso of the body which is attached to a curved rail which varies the angle of the carriage relative to the ground as the user forces the carriage or seat upwardly, and thereby increases the force on the legs of the user as the user propels the chair upwardly. In this apparatus the rate of increase of the force on the legs of the user is pre-determined by the fixed angle of the discretely curved rail or incline and the force cannot be varied by the operator at any given position. The weight of the body at the operator is used as the resistance or force against which the operator exercises.
U.S. Pat. No. 3,998,454 and U.S. Pat. No. 3,858,873 disclose a force applying member for use in exercising machines in which the force transmitted to various parts of the body is varied. The force is varied by a spiral pulley connected to the rotating force transference member which varies the lever arm applied to a cable having vertically suspended weights at one end, the lever arm being dependent upon the radius of the spiral pulley at any selected position. The force cannot be increased by the user of the machine while using the machine since it is necessary for the user of the machine to dismount and place more weights on the cable to increase the force on the user.
U.S. Pat. No. 3,010,720 discloses an exercise rack which the user sits upon to do sit-ups which can be inclined to vary the angle of the body of the user relative to the ground to vary the force on the user's body. The angle of inclination must be adjusted prior to the user mounting the machine and cannot be varied after the user is actually exercising on the machine.
U.S. Pat. No. 2,436,987 discloses an exercising apparatus using an inclined exercising board upon which the user lies in a prone position. The angle of inclination of the exercising board can be varied to increase or decrease the stress on the user while the user is doing sit-ups or touching his toes from a prone position. The user must pre-set the board to the desired position and cannot vary its position while actually using the board.
U.S. Pat. No. 1,547,268 discloses an arm which can be inclined with the horizontal and which has a movable weight thereon, the movable weight having a cable connected thereto for transmitting force to various parts of the body of the user. The angle of inclination of the arm with the horizontal is varied by fixing the upper end of the arm on a stationary arc having a series of ratchet teeth thereon. A bolt connectable to the upper end of the movable arm engages the ratchet teeth on the arc to fix the angle of inclination of the movable arm. The movable arm cannot be moved while the operator of the machine is actually exercising with the machine, and it is necessary for the operator to cease exercising and pre-position the movable arm to established a fixed weight or force whose resistance must be over come by the user of the apparatus.
U.S. Pat. No. 682,988 discloses an exercising or rowing machine in which the force on the body of the user is varied by inclining the body of the user to various selected positions. However, the inclination cannot be accomplished by the user during operating the machine and requires that the user dismount from the machine and set the angle of inclination.